My 72z had a problem just very similar to yours, I looked at the schematic wiring diagram to analyze the problem and it did not make any sense. Finally I just decided to clean the turn signal contacts and that solved the problem. Apparently many lines go through the turn signal switch that is not apparent in the schematic. Another thing you can do is just swing the switch between left and right turn signaling many times at once until the switch contacts are cleaned in that manner. This is a lot easier than taking it apart. It worked for me.